1905.] 



NATURAL SCIENCES OF PHILADELPHIA. 



297 



From the lower side of the notopodial tubercle arises a tuft of iri- 

 descent hairs which spring from a curved line reaching from the anterior 

 margin of the tubercle upward and backward to the base of the noto- 

 podial cirrus, which occupies a posterior position. These capillary 

 setas spread in a flowing plume outward, backward and upward, cover- 

 ing the sides of the body and the neuropodia. Compared with the cor- 

 responding structures in A. aculeata they present numerous differences- 

 In the first place they are fewer, about one-third longer and spread 

 more widely, irregularly and in greater disorder from the sides. In our 

 species they are much softer and less harsh and rigid— a difference 

 which becomes especially evident if they are brushed forward and 

 released, when those of A. aculeata spring quickly back to position, 

 while those of A. hastata return slowy and gently. But the most strik- 

 ing difference is in color, ours being far less brilliant than the European 

 species. Wlien placed in corresponding positions with reference to the 

 light and the observer's eye, namely, wdth the caudal 

 end toward the light and the head toward and below 

 the observer, the marginal hairs of A. aculeata appear 

 of a beautiful burnished golden green color, rich golden 

 predominating toward the base and a fine viridian 

 green in the outer half, the intensity of the display 

 being enhanced by the great number and relatively 

 compact arrangement of the hairs, while the general 

 effect of those of A. hastata varies from a pearl color to 

 a richer bronzy red in different individuals. In the 

 paler variety the hairs appear purplish-blue, toward 

 the base changing to a delicate red, and toward the tip 

 to a varied mixture of reddish-purple and bluish-green 

 which differs as the glancing hght strikes particular 

 hairs at different angles. Owing to the more open, 

 spreading arrangement of the hairs in our species this 

 dispersal of the colors is more evident. When viewed 

 at other angles or by transmitted light the distribution 

 of colors differs. 



The two tufts of large notopodial spines arise, as 

 in most species, one just anterior to the dorsal cirrus, 

 the other, separated by a short interval, higher on 

 the dorsum. The first consists of about 4 and the 

 second of about 6 or 7 long, curved, soft, coarse and 

 brownish setae which, after perforating the dorsal felt, e\irve, most 

 of them perfectly free from and above the latter, caudad and 



Fig. 4.— Tip 

 of notopodial 

 seta. X 250. 



